All-solid-state battery using composite solid electrolyte

Abstract

The present application relates to the technical field of lithium ion battery, disclose the full solid battery of composite solid electrolyte is adopted, the electrolyte is composed of polyethylene glycol methyl ether methyl methacrylate, 5wt%~10wt% polyethylene glycol dimethyl methacrylate crosslinking agent, 30wt%~70wt% NASICON type LAGP nanoparticles and lithium salt.The present application adopts in situ photopolymerization process, the composite material is used as unified medium and is applied to positive electrode adhesive and electrolyte layer simultaneously, realizes synchronous crosslinking solidification under the condition of pressure, constructs continuous three-dimensional ion transmission network and integrated interface of chemical bonding.The technical scheme effectively solves the problem of high solid-solid interface contact impedance and structural collapse caused by electrode cycle volume expansion, can effectively absorb the volume expansion stress generated in the process of charge and discharge of positive active material, improves the ionic conductivity, mechanical strength, high temperature resistance and long cycle stability of full solid battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to an all-solid-state battery using a composite solid electrolyte. Background Technology

[0002] With the rapid development of new energy vehicles and portable electronic devices, the market has placed higher demands on the energy density and safety of energy storage devices. Traditional lithium-ion batteries face major safety hazards due to their use of flammable and leak-prone organic liquid electrolytes, and their energy density improvement has reached a theoretical bottleneck. All-solid-state batteries (ASSBs), by using non-flammable solid electrolytes instead of liquid electrolytes, fundamentally improve battery safety and are compatible with high-voltage positive electrodes and lithium metal negative electrodes, becoming the mainstream technology for next-generation high-energy batteries.

[0003] However, the commercial application of all-solid-state batteries still faces severe technical challenges, the most critical of which lies in the contact stability and ion transport efficiency of the solid-solid interface. Unlike liquid electrolytes, which can fully wet electrode particles, solid electrolytes rely primarily on physical contact with electrode active materials, resulting in a limited interfacial contact area and extremely high interfacial impedance. In traditional battery manufacturing processes, non-ionic conductive polymers (such as polyvinylidene fluoride, PVDF) are typically used as positive electrode binders, which further blocks ion transport channels on the surface of active material particles and increases polarization. Furthermore, positive electrode active materials (such as high-nickel ternary materials) undergo volume expansion and contraction during long-term charge-discharge cycles. This repeated volume effect easily damages the physical interface maintained solely by mechanical pressure, leading to the pulverization and detachment of active material particles and the peeling of the electrolyte layer from the electrode layer, resulting in rapid capacity decay.

[0004] To improve interfacial contact and ionic conductivity, researchers have attempted to develop composite solid electrolytes (CSEs), which involve introducing inorganic fast ion conductors into a polymer matrix. While this strategy combines the flexibility of polymers with the high conductivity of ceramics to some extent, existing composite electrolyte solutions often struggle to balance mechanical strength and electrochemical performance. On one hand, if the inorganic filler content is too low, it is difficult to form a continuous ion-conducting network; if the content is too high, the material becomes brittle, its processing performance deteriorates, and it is difficult to adapt to changes in electrode volume. On the other hand, conventional linear polymer matrices (such as linear polyethylene glycol derivatives) are prone to softening and creep at high temperatures, losing not only their mechanical support capacity but also easily triggering oxidative decomposition side reactions at the interface, limiting the lifespan and reliability of all-solid-state batteries under high-temperature conditions. Therefore, there is an urgent need to develop a novel solid electrolyte system and its construction process that can simultaneously address internal electrode ion conductivity, interfacial physicochemical bonding stability, and high-temperature mechanical integrity. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an all-solid-state battery using a composite solid electrolyte, which solves the problems of high solid-solid interface contact impedance, difficulty in balancing electrolyte membrane mechanical strength and ionic conductivity, and serious impact on battery cycle life and rate performance caused by physical delamination of the interface due to electrode cycling volume effect in existing all-solid-state batteries.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The core technical solution of this invention lies in constructing a structurally integrated all-solid-state battery system. This system employs a composite solid electrolyte with the same chemical composition within the positive electrode active material layer (acting as a binder) and in the solid electrolyte layer between the positive and negative electrodes. This composite solid electrolyte is an inorganic-organic composite material, and its microstructure is characterized by:

[0008] Nanoparticles, as a highly ionicly conductive phase, are uniformly dispersed in a polyether network formed by crosslinking polyethylene glycol methyl ether methacrylate and polyethylene glycol dimethacrylate.

[0009] In terms of composition, this invention strictly controls the ratio of inorganic to organic phases. Specifically, the content of LAGP nanoparticles is set between 30 wt% and 70 wt% of the solid content. This range ensures that the material macroscopically combines the high ion transport capacity of inorganic materials with the mechanical flexibility of polymer materials. Simultaneously, polyethylene glycol dimethacrylate, as a crosslinking agent, is controlled at 5 wt% to 10 wt% of the solid content, and, in conjunction with a specific lithium salt concentration ([Li] / [EO] = 1 / 16 to 1 / 24), is used to construct a three-dimensional crosslinked network framework with sufficient mechanical strength and thermal stability.

[0010] In terms of manufacturing process, this invention employs an in-situ curing strategy of first forming and then polymerizing. First, a solvent-containing composite slurry is applied to both the positive electrode coating and the electrolyte layer coating, and a drying process completely removes the solvent, forming a dry pre-fabricated layer containing unreacted active double bonds. Subsequently, the negative electrode is laminated and pressure of 0.5 MPa to 2.0 MPa is applied to establish dense physical contact between the layers. Finally, ultraviolet light is applied while maintaining pressure to initiate an in-situ free radical polymerization reaction. This process ensures that the polymerization reaction occurs not only within each layer but also at the interface between the positive electrode layer and the electrolyte layer, solidifying the two layers into an inseparable whole through chemical bonding.

[0011] This invention provides an all-solid-state battery employing a composite solid electrolyte. It offers the following advantages:

[0012] 1. This invention utilizes an in-situ photopolymerization process to simultaneously crosslink and solidify the positive electrode active material layer and the solid electrolyte layer under pressure, forming chemical bonds at the interface. This continuous three-dimensional network structure, constructed from 5wt% to 10wt% crosslinking agent, effectively absorbs the volume expansion stress generated by the positive electrode active material during charging and discharging, preventing internal structural collapse of the electrode layer and physical delamination between layers, thereby enabling the battery to maintain a high capacity retention rate during long-term cycling.

[0013] 2. This invention strictly controls the content of NASICON-type LAGP nanoparticles within a high proportion range of 30wt% to 70wt%, and applies them as a unified ion-conducting medium to both the electrode binder and the solid electrolyte layer. This design not only ensures that the composite material itself has high ion conductivity, but also constructs a seamless ion transport channel between the electrode particles and the electrolyte layer, eliminating the interfacial resistance caused by the contact of heterogeneous materials and improving the rate charge-discharge performance of the all-solid-state battery.

[0014] 3. The composite solid electrolyte used in this invention forms a thermally stable interpenetrating polymer network through the cross-linking reaction of polyethylene glycol methyl ether methacrylate and polyethylene glycol dimethacrylate. This cross-linked network structure can effectively inhibit the creep of polymer chain segments and the thermal degradation of electrolyte components under high temperature conditions, and reduce chemical side reactions at the electrode interface, thereby giving the all-solid-state battery a high-temperature capacity retention rate. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0016] raw material:

[0017] Polyethylene glycol methyl ether methacrylate (PEGMEMA), CAS number 26915-72-0, has a number-average molecular weight Mn of approximately 500 g / mol;

[0018] Polyethylene glycol dimethacrylate (PEGDM), CAS number 25852-47-5, has a number-average molecular weight (Mn) of approximately 750 g / mol.

[0019] Preparation Examples 1-6:

[0020] Preparation Example 1:

[0021] This preparation example is used for synthesis. Nanoparticles. According to stoichiometry. Lithium carbonate, alumina, germanium dioxide, and ammonium dihydrogen phosphate were weighed, with lithium carbonate in excess at 5 wt% to compensate for high-temperature volatilization losses. The raw materials were mixed and ball-milled in an agate jar for 4 hours at 300 rpm. The mixture was then placed in an alumina crucible and pre-sintered in a muffle furnace at 650°C for 4 hours to decompose the carbonates and ammonium salts in the raw materials. The pre-sintered powder was ball-milled again, pressed into sheets, and sintered at 900°C for 12 hours to obtain dense LAGP ceramic blocks. After pulverizing the ceramic blocks, high-energy wet ball milling was performed in a planetary ball mill using ethanol as the medium at a ball-to-material ratio of 20:1, a rotation speed of 500 rpm, and a milling time of 48 hours. After ball milling, the slurry was dried in a vacuum drying oven at 80°C for 12 hours, ground, and sieved to obtain NASICON-type LAGP nanoparticles with an average particle size (D50) of 200 nm.

[0022] Preparation Example 2:

[0023] This preparation example is used to prepare a composite solid electrolyte precursor slurry (component A content 50 wt%, component D content 7.5 wt%, as a preferred example for comparison). In an argon glove box, polyethylene glycol methyl ether methacrylate (PEGMEMA) and polyethylene glycol dimethacrylate (PEGDM) were weighed, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was added, stirring until the lithium salt was completely dissolved. Anhydrous acetonitrile was then added as a solvent, followed by the LAGP nanoparticles obtained in Preparation Example 1, and finally the photoinitiator HMPP. The mixture was placed in a planetary stirrer and stirred at 2000 rpm for 20 minutes to obtain a uniformly dispersed composite solid electrolyte precursor slurry. The amount of each component added is calculated as a percentage of the total mass of solids after solvent removal: LAGP nanoparticles (component A) account for 50 wt%, PEGDM crosslinking agent (component D) accounts for 7.5 wt%, photoinitiator accounts for 1.0 wt% of the total mass of organic monomers, and the balance is PEGMEMA monomer (component B) and LiTFSI (component C); the amount of LiTFSI added is controlled so that the molar ratio of lithium ions to ethylene oxide units in PEGMEMA [Li] / [EO] is 1 / 20.

[0024] Preparation Example 3:

[0025] This preparation example is used to prepare a composite solid electrolyte precursor slurry (component A content 30wt%, low inorganic content boundary). The preparation steps are the same as in Preparation Example 2, the only difference being the adjustment of the proportions of each component. The amount of each component added is calculated as a percentage of the total mass of solids after solvent removal: LAGP nanoparticles (component A) account for 30wt%, PEGDM crosslinking agent (component D) accounts for 7.5wt%, photoinitiator accounts for 1.0wt% of the total mass of organic monomers, and the balance is PEGMEMA monomer (component B) and LiTFSI (component C); the [Li] / [EO] molar ratio is maintained at 1 / 20.

[0026] Preparation Example 4:

[0027] This preparation example is used to prepare a composite solid electrolyte precursor slurry (component A content 70wt%, high inorganic content boundary). The preparation steps are the same as in Preparation Example 2, the only difference being the adjustment of the proportions of each component. The amount of each component added is calculated as a percentage of the total mass of solids after solvent removal: LAGP nanoparticles (component A) account for 70wt%, PEGDM crosslinking agent (component D) accounts for 7.5wt%, photoinitiator accounts for 1.0wt% of the total mass of organic monomers, and the balance is PEGMEMA monomer (component B) and LiTFSI (component C); the [Li] / [EO] molar ratio is maintained at 1 / 20.

[0028] Preparation Example 5:

[0029] This preparation example is used to prepare a composite solid electrolyte precursor slurry (component D content 5wt%, low crosslinking degree boundary). The preparation steps are the same as in Preparation Example 2, except that the proportions of each component are adjusted. The amount of each component added is calculated as a percentage of the total mass of solids after solvent removal: LAGP nanoparticles (component A) account for 50wt%, PEGDM crosslinking agent (component D) accounts for 5wt%, photoinitiator accounts for 1.0wt% of the total mass of organic monomers, and the balance is PEGMEMA monomer (component B) and LiTFSI (component C); the [Li] / [EO] molar ratio is maintained at 1 / 20.

[0030] Preparation Example 6:

[0031] This preparation example is used to prepare a composite solid electrolyte precursor slurry (component D content 10wt%, high crosslinking degree boundary). The preparation steps are the same as in Preparation Example 2, except that the proportions of each component are adjusted. The amount of each component added is calculated as a percentage of the total mass of solids after solvent removal: LAGP nanoparticles (component A) account for 50wt%, PEGDM crosslinking agent (component D) accounts for 10wt%, photoinitiator accounts for 1.0wt% of the total mass of organic monomers, and the balance is PEGMEMA monomer (component B) and LiTFSI (component C); the [Li] / [EO] molar ratio is maintained at 1 / 20.

[0032] Examples 1-7:

[0033] Example 1:

[0034] This embodiment provides an all-solid-state battery using a composite solid electrolyte, including the following steps:

[0035] (1) Preparation of the positive electrode active material layer: The positive electrode active material NCM811, the conductive agent acetylene black, and the composite solid electrolyte precursor slurry obtained in Preparation Example 2 were mixed, and an appropriate amount of acetonitrile was added to adjust the viscosity. The mass ratio of NCM811, acetylene black, and the solid components in the precursor slurry was 90:3:7. The mixed slurry was coated onto the surface of the carbon-coated aluminum foil current collector and placed in a forced-air drying oven. It was dried at 60°C for 30 minutes to completely remove the solvent, thus obtaining a dry positive electrode layer containing unpolymerized double bonds.

[0036] (2) Coating and drying of the solid electrolyte layer: The composite solid electrolyte precursor slurry obtained in Example 2 was directly coated onto the surface of the above-mentioned dried positive electrode layer, and the wet film thickness was controlled. Then it was placed in a vacuum oven and dried for 4 hours at 60°C and a vacuum degree of -0.095MPa to remove the solvent, and a dry solid electrolyte layer with a thickness of about 30μm was obtained.

[0037] (3) Battery assembly and lamination: In an argon glove box, a 30 μm thick lithium metal negative electrode foil was placed on the surface of a dry solid electrolyte layer to form a laminate. A flatbed hot press was used to apply a surface pressure of 1.0 MPa to the laminate at 25°C for 2 minutes to ensure dense contact between the layers.

[0038] (4) In-situ photopolymerization: While maintaining pressure, irradiate from the positive electrode side using an LED surface light source with a center wavelength of 365nm, and set the light intensity to [value missing]. The irradiation time is 15 minutes. Ultraviolet light penetrates the positive electrode layer and electrolyte layer, initiating an in-situ polymerization reaction between monomers and crosslinking agents, completing the integrated curing and encapsulation of the battery.

[0039] Example 2:

[0040] This embodiment provides an all-solid-state battery using a composite solid electrolyte, including the following steps: except that the precursor slurry used in steps (1) and (2) is replaced with the slurry obtained in Preparation Example 3 (containing 30wt% LAGP), the other preparation steps, process parameters and raw material ratios are consistent with those in Example 1.

[0041] Example 3:

[0042] This embodiment provides an all-solid-state battery using a composite solid electrolyte, including the following steps: except that the precursor slurry used in steps (1) and (2) is replaced with the slurry obtained in Preparation Example 4 (containing 70wt% LAGP), the other preparation steps, process parameters and raw material ratios are consistent with those in Example 1.

[0043] Example 4:

[0044] This embodiment provides an all-solid-state battery using a composite solid electrolyte, including the following steps: except that the precursor slurry used in steps (1) and (2) is replaced with the slurry obtained in Preparation Example 5 (containing 5wt% PEGDM), the other preparation steps, process parameters and raw material ratios are consistent with those in Example 1.

[0045] Example 5:

[0046] This embodiment provides an all-solid-state battery using a composite solid electrolyte, including the following steps: except that the precursor slurry used in steps (1) and (2) is replaced with the slurry obtained in Preparation Example 6 (containing 10wt% PEGDM), the other preparation steps, process parameters and raw material ratios are consistent with those in Example 1.

[0047] Example 6:

[0048] This embodiment provides an all-solid-state battery using a composite solid electrolyte, including the following steps:

[0049] (1) Preparation of positive electrode active material layer: The raw material ratio and slurry selection (preparation example 2) are the same as in example 1, the drying temperature is adjusted to 50℃ and the drying time is 40 minutes.

[0050] (2) Coating and drying of solid electrolyte layer: The slurry is the same as that in Example 1, the vacuum drying temperature is adjusted to 50°C, and the drying time is 6 hours.

[0051] (3) Battery assembly and lamination: The lamination pressure is adjusted to 0.5MPa and the holding time is 5 minutes.

[0052] (4) In-situ photopolymerization: The light intensity is adjusted to The irradiation time was adjusted to 30 minutes.

[0053] Example 7:

[0054] This embodiment provides an all-solid-state battery using a composite solid electrolyte, including the following steps:

[0055] (1) Preparation of positive electrode active material layer: The raw material ratio and slurry selection (preparation example 2) are the same as in example 1, the drying temperature is adjusted to 70℃ and the drying time is 20 minutes.

[0056] (2) Coating and drying of solid electrolyte layer: The slurry is the same as that in Example 1, the vacuum drying temperature is adjusted to 60°C, and the drying time is 3 hours.

[0057] (3) Battery assembly and lamination: The lamination pressure is adjusted to 2.0 MPa and the holding time is 1 minute.

[0058] (4) In-situ photopolymerization: The light intensity is adjusted to The irradiation time was adjusted to 10 minutes.

[0059] Comparative Examples 1-5:

[0060] Comparative Example 1:

[0061] This comparative example is used to verify the necessity of the crosslinking agent and the three-dimensional network structure. Compared with Example 1, the difference is that when preparing the composite solid electrolyte precursor slurry, polyethylene glycol dimethacrylate (PEGDM) crosslinking agent is not added, and the reduced mass fraction is replaced with polyethylene glycol methyl ether methacrylate (PEGMEMA) monomer, so that the slurry forms a linear polymer matrix instead of a three-dimensional crosslinked network structure after curing. The other raw material ratios, preparation steps and process parameters are the same.

[0062] Comparative Example 2:

[0063] This comparative example is used to verify the necessity of the inorganic nanoparticle content (30 wt%). The difference from Example 1 is that the amount of LAGP nanoparticles added was adjusted to account for 10 wt% of the total solid mass after solvent removal when preparing the composite solid electrolyte precursor slurry. The content of organic components (PEGMEMA and PEGDM) was increased accordingly to make up the balance. The other raw material ratios, preparation steps and process parameters are the same.

[0064] Comparative Example 3:

[0065] This comparative example is used to verify the necessity of the inorganic nanoparticle content (70 wt%). Compared with Example 1, the difference is that when preparing the composite solid electrolyte precursor slurry, the amount of LAGP nanoparticles added was adjusted to account for 85 wt% of the total solid mass after solvent removal, and the content of organic components (PEGMEMA and PEGDM) was reduced accordingly. The other raw material ratios, preparation steps and process parameters are the same.

[0066] Comparative Example 4:

[0067] This comparative example is used to verify the necessity of using an integrated ion-conductive binder inside the positive electrode (compared to traditional non-conductive binders). The difference from Example 1 is that in step (1), during the preparation of the positive electrode active material layer, a composite solid electrolyte precursor slurry is not used; instead, polyvinylidene fluoride (PVDF) is used as the binder. The positive electrode ratio is adjusted to NCM811:acetylene black:PVDF = 90:5:5, and N-methylpyrrolidone (NMP) is used as the solvent for coating and drying. The preparation of the solid electrolyte layer and the battery assembly process in steps (2) to (4) are consistent with those in Example 1.

[0068] Comparative Example 5:

[0069] This comparative example is used to verify the necessity of in-situ photopolymerization for interfacial performance (comparing to stepwise curing processes). Compared with Example 1, the difference is that the curing order has been changed. Specifically, after drying the positive electrode layer in step (1) and the electrolyte layer in step (2), the positive electrode layer and the electrolyte layer are first irradiated with ultraviolet light to cure them completely on their own. Then, step (3) is performed to laminate the cured solid electrolyte membrane with the cured positive electrode and negative electrode, without performing the subsequent step (4) in-situ photopolymerization. The remaining raw material ratios and parameters are the same.

[0070] Test Examples 1-5:

[0071] Test Example 1: Physical Property Testing of Composite Solid Electrolyte Membranes

[0072] Experimental steps:

[0073] Ionic conductivity testing: The electrochemical impedance spectroscopy (EIS) method was used for measurement. The composite solid electrolyte precursor slurries prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were coated between two stainless steel sheets to a thickness of 100 μm. They were then cured under their respective photocuring or drying conditions to form films, assembling them into a stainless steel / electrolyte membrane / stainless steel structure blocking battery. Testing was conducted using an electrochemical workstation (model: AutolabPGSTAT302N) at a constant temperature of 25°C, with a frequency scan range of 0.1 Hz to 1 MHz and an amplitude of 10 mV. The bulk resistance was determined based on the intercept of the high-frequency arc of the Nyquist plot with the real axis. And through the formula Calculate ionic conductivity ,in For film thickness, This represents the electrode contact area.

[0074] Mechanical property testing: Tensile properties were tested using a universal testing machine. The above-mentioned slurries were coated into polytetrafluoroethylene molds, cured, and then demolded and cut into strips 10 mm wide and 50 mm long. At room temperature, a tensile rate of 5 mm / min was set, and the stress-strain curves of the strips were recorded during the tensile process until the strips broke. The tensile strength (MPa) and elongation at break (%) of each electrolyte membrane were obtained.

[0075] Experimental data:

[0076] Table 1. Test results of ionic conductivity and mechanical properties of composite solid electrolyte membranes for each group

[0077]

[0078] (Note: Due to the excessively high content of inorganic fillers, the film formed by the Comparative Example 3 sample was extremely brittle and could not be fully subjected to standard tensile testing, therefore no effective mechanical strength data was obtained.)

[0079] in conclusion:

[0080] The composite solid electrolyte membranes prepared in Examples 1 to 7 achieved a good balance between ion conductivity and mechanical properties. In Example 1, with the synergistic effect of 50 wt% LAGP content and 7.5 wt% crosslinking agent content, the room temperature ion conductivity reached [value missing]. It also maintained a tensile strength of 4.82 MPa and an elongation at break of 62.4%.

[0081] Comparative data from Example 1 and Comparative Example 1 (without crosslinking agent) show that although their ionic conductivity is similar, the tensile strength of the linear polymer matrix (Comparative Example 1) lacking crosslinking agent is only 0.42 MPa, exhibiting a gel-like state and severe creep. This confirms that introducing PEGDM to construct a three-dimensional crosslinked network is a key factor in endowing the electrolyte membrane with sufficient mechanical strength to suppress lithium dendrite growth and withstand electrode volume changes.

[0082] Comparative data from Examples 2 and 3 and Comparative Examples 2 and 3 show that the content of LAGP nanoparticles affects performance. While Comparative Example 2 (10 wt% LAGP) exhibits good flexibility, its ionic conductivity drops by orders of magnitude. The first method cannot meet the requirements of high-rate batteries; while the second method (85wt% LAGP) has the highest conductivity, but the material loses its flexibility and exhibits extremely high brittleness, making it unsuitable for the winding or lamination assembly process of all-solid-state batteries. This invention limits the inorganic particles to the range of 30wt% to 70wt%, effectively resolving the contradiction between high ionic conductivity and processability.

[0083] Furthermore, data from Examples 4 and 5 show that adjusting the crosslinking agent content can finely tune the stiffness and toughness of the material, with a range of 5 wt% to 10 wt% ensuring that the material maintains high strength without losing excessive ion transport chain mobility.

[0084] Test Example 2: Electrochemical Stability Window Test

[0085] Experimental steps:

[0086] The electrochemical oxidative decomposition potential of the composite solid electrolyte membrane was determined using a linear sweep voltammetry method.

[0087] The composite solid electrolyte precursor slurries prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were coated onto stainless steel sheets and then used to form electrolyte membranes according to their respective photocuring or drying processes. In an argon-filled glove box (water and oxygen content <0.1 ppm), lithium metal sheets were used as counter and reference electrodes, and stainless steel sheets were used as working electrodes to assemble an asymmetric blocking battery with a Li / electrolyte membrane / SS structure.

[0088] The tests were conducted using an electrochemical workstation (model: Autolab PGSTAT302N) under isothermal conditions at 25°C. The scan voltage range was set from the open-circuit voltage (OCV) to... The scan rate was set to 0.1 mV / s. The curve of current versus voltage was recorded, and the onset potential where the current density increases sharply and irreversibly was defined as the oxidative decomposition potential of the electrolyte. (Judgment criteria: current density exceeds) (Voltage value at that time).

[0089] Experimental data:

[0090] Table 2. Electrochemical oxidation decomposition potential test results of composite solid electrolyte membranes in each group

[0091]

[0092] Note: The "-" symbol in the oxidative decomposition potential column indicates that no experimental data was generated, and in the remarks column it indicates that the item is empty.

[0093] in conclusion:

[0094] The oxidation decomposition potentials of Examples 1 to 7 are generally above 4.8V, with Example 1 of the preferred formulation reaching 5.18V. This value is higher than the typical oxidation limit of conventional polyether (PEO) electrolytes (approximately 3.9V to 4.2V), indicating that this composite electrolyte is compatible with high-voltage cathode materials such as NCM811 (the charging cut-off voltage is typically 4.2V to 4.3V).

[0095] Comparing the data differences between Example 1 and Comparative Example 1 (4.35V) confirms the crucial role of constructing a three-dimensional cross-linked network. In the linear polymer system of Comparative Example 1, the polyether segments exhibit high degrees of freedom of movement and are highly responsive to anions (…). The weak binding ability of the polymer chain leads to easy oxidative degradation of the polymer ends at high potentials. However, the dense network structure formed by the PEGDM crosslinking agent in Example 1 restricts the excessive movement of polymer chain segments on the one hand, and hinders the migration of anions to the positive electrode surface through steric hindrance, thereby effectively improving the high voltage resistance.

[0096] The differences in data between Examples 1 and 2 (4.82V) and Comparative Example 2 (4.56V) demonstrate the influence of inorganic filler content. High content (above 30wt%) of NASICON-type LAGP nanoparticles not only act as ion conductors but also as solid fillers, physically blocking the direct contact area between the polymer and the oxidizing electrode, and stabilizing anions at the interface through Lewis acid-base interactions. When the LAGP content is too low (e.g., 10wt% in Comparative Example 2), this protective effect weakens, leading to a narrower electrochemical window.

[0097] In summary, this invention broadens the electrochemical stability window of polymer-based solid electrolytes through the synergistic effect of high-content inorganic nanoparticles and cross-linked polymer networks, enabling them to meet the operational requirements of high-energy-density all-solid-state batteries.

[0098] Test Example 3: Cycle Performance Test of All-Solid-State Battery

[0099] Experimental steps:

[0100] The all-solid-state coin cells prepared in Examples 1 to 7 and Comparative Examples 1 to 5 were subjected to constant current charge-discharge cycle tests. The LANDCT2001A battery testing system was used for testing, and the ambient temperature was controlled at 25±1℃.

[0101] The specific test procedure is set as follows: The charge / discharge voltage range is set to 3.0V~4.2V. First, activation is performed: the first charge / discharge cycle is carried out at a rate of 0.05C, and the specific capacity and coulombic efficiency of the first discharge cycle are recorded.

[0102] A long-cycle test was then conducted: the device was charged at a constant current of 0.5C until the voltage reached 4.2V, then switched to constant voltage charging with a cutoff current of 0.05C; after resting for 10 minutes, it was discharged at a constant current of 0.5C to 3.0V. This charge-discharge process was repeated 200 times.

[0103] The system automatically records the discharge capacity of each cycle and calculates the discharge capacity of the [number]th cycle according to the formula. Capacity retention rate (%) for the next cycle:

[0104] in, For capacity retention, For the first Discharge capacity per cycle, The first discharge capacity (mAh / g) at a 0.5C rate.

[0105] Experimental data:

[0106] Table 3. Test data of 0.5C cycle performance of all-solid-state batteries at 25℃

[0107]

[0108] (Note: Comparative Example 1 experienced a voltage drop around the 85th cycle, which was determined to be an internal micro-short circuit; Comparative Example 3 did not obtain effective battery data because the electrolyte layer was too brittle to withstand the lamination stress.)

[0109] The "-" symbol indicates that no experimental data was generated.

[0110] in conclusion:

[0111] Example 1 exhibits optimal cycle stability, with a capacity retention of up to 91.8% after 200 cycles. This is attributed to its unique integrated cathode-electrolyte structure. The composite electrolyte inside the cathode, acting as a binder, is chemically homologous to the external solid electrolyte layer and forms a covalent bond at the interface through in-situ photopolymerization. This structure eliminates the physical interface present in conventional batteries, ensuring that even if the electrode material expands or contracts during long cycles, the transport channels remain continuous and intact, without the increase in contact resistance caused by interface peeling.

[0112] The initial discharge capacity and cycle retention rate of Comparative Example 4 (PVDF binder, retention rate 74.1%) were both lower than those of Example 1. While PVDF, as an insulating component, provides adhesion, it blocks ion transport on the surface of the active material particles, relying solely on point contact for conductivity, leading to increased polarization. In contrast, the composite electrolyte in Example 1, acting as a binder, constructed a three-dimensional continuous ion-conducting network around the active material particles, effectively reducing charge transfer impedance.

[0113] The comparison between Comparative Example 5 (stepwise curing, 78.3% retention rate) and Example 1 directly confirms the value of the in-situ photopolymerization process. Although the material compositions of the two are completely identical, the positive electrode layer and the electrolyte layer in Comparative Example 5 only have physical contact. Under the stress of repeated volume changes caused by charge-discharge cycles, the physical contact interface gradually loosens and micropores are generated, leading to obstructed lithium-ion transport and accelerated capacity decay. In contrast, Example 1 achieves mechanical structural integrity through interfacial chemical bonding, making it more resistant to mechanical stress.

[0114] Data from Comparative Example 1 (without crosslinking agent, early failure) show that linear polymers alone cannot maintain structural stability under high temperatures or long-term cycling. Linear polymers are prone to plastic deformation (creep) during repeated lithium-ion insertion and extraction, leading to the detachment of the positive electrode active material particles from the conductive agent (pulverization), and even short circuits caused by lithium dendrites piercing due to insufficient mechanical strength. The rigid network constructed with 5wt%–10wt% crosslinking agent in Example 1 effectively suppressed this type of structural collapse.

[0115] Test Example 4: High-Temperature Storage Performance Test

[0116] Experimental steps:

[0117] This test aims to evaluate the battery's charge retention and capacity recovery capabilities under high-temperature conditions, thereby characterizing the thermal stability and resistance to interfacial side reactions of the composite solid electrolyte.

[0118] All-solid-state batteries prepared in Examples 1 to 7, as well as Comparative Examples 1, 2, 4, and 5, were selected as test subjects.

[0119] The specific operating procedure is as follows:

[0120] Initial capacity determination: At 25℃, the battery was charged at a constant current of 0.5C to 4.2V, then switched to constant voltage charging to 0.05C (cutoff). After standing for 10 minutes, it was discharged at a constant current of 0.5C to 3.0V. The discharge capacity of this discharge was recorded as the initial discharge capacity (mAh / g).

[0121] High-temperature storage: Recharge the battery to 4.2V (100% SOC) and place it in a temperature-controlled chamber. Raise the temperature to 60℃ and maintain it for 7 days (168 hours).

[0122] Charge retention test: After storage, the battery was removed and allowed to cool naturally at room temperature for 2 hours. It was then discharged directly at a constant current of 0.5C to 3.0V, and the discharge capacity was recorded as the retention capacity after storage.

[0123] Capacity recovery rate test: The above battery was subjected to a standard charge-discharge cycle (0.5C charge / 0.5C discharge) at 25°C, and the discharge capacity was recorded as the recovered discharge capacity.

[0124] Calculation formula: Charge retention rate:

[0125] Capacity recovery rate:

[0126] Experimental data:

[0127] Table 4. Performance test data of all-solid-state batteries after 7 days of storage at 60℃

[0128]

[0129] Note: The "-" symbol indicates that the content of this item is empty.

[0130] in conclusion:

[0131] After storage at 60°C for 7 days, Examples 1 and 5 showed capacity recovery rates of 96.8% and 97.5%, respectively. This confirms that the interpenetrating polymer network structure formed by the PEGDM crosslinking agent effectively suppresses the creep behavior of polymer segments at high temperatures. Under the harsh conditions of high temperature and high voltage (60°C, 4.2V), the crosslinking structure restricts the movement of free groups in the electrolyte, reduces the probability of oxidative decomposition side reactions between the electrolyte and the surface of the positive electrode active material, and thus reduces irreversible lithium-ion consumption.

[0132] Comparative Example 1 (without crosslinking agent) showed a charge retention rate of only 12.5%, and the capacity was almost impossible to recover. This indicates that the linear polyethylene glycol derivative underwent severe softening and even rheological changes at 60°C, leading to the failure of contact between the positive electrode particles and the conductive network, and even micro-short circuits caused by local electrolyte thinning, resulting in severe self-discharge.

[0133] Comparing the data differences between Example 1 and Comparative Example 5 (stepwise curing, capacity recovery rate 86.3%) reveals the impact of interface bonding mode on thermal stability. During high-temperature storage and subsequent cooling, different material layers undergo thermal expansion and contraction. The chemically bonded interface of Example 1 can withstand this thermal stress, maintaining unobstructed ion transport channels at the interface; while the physical contact interface of Comparative Example 5 is prone to generating microscopic voids during thermal expansion and contraction cycles, causing some active materials to become dead lithium due to loss of ion contact, resulting in permanent capacity loss.

[0134] Furthermore, Example 3 (70% high content of inorganic particles) exhibited an extremely high capacity recovery rate (97.1%), indicating that a high proportion of inorganic ceramic fillers helps to improve the overall thermal stability of the composite material and reduce the volume percentage of the polymer matrix that is degraded by heat.

[0135] Test Example 5: Rate Charge / Discharge Performance Test

[0136] Experimental steps:

[0137] This test aims to evaluate the discharge capacity of all-solid-state batteries at different current densities, thereby characterizing the lithium-ion transport kinetics within and at the electrode interface.

[0138] All-solid-state batteries prepared in Examples 1 to 7, as well as Comparative Examples 2, 4, and 5, were selected as test subjects. (Note: Comparative Example 1 failed in the cycle test because it could not withstand high current polarization, and Comparative Example 3 could not be tested because its electrode was brittle. Therefore, it was not included in this test.)

[0139] The LANDCT2001A battery testing system was used for testing in a constant temperature environment of 25°C. The voltage range was set to 3.0V to 4.2V. The test program was set with the following step rate settings:

[0140] Five constant current charge-discharge cycles at 0.1C were performed, and the capacity of the last discharge cycle was recorded as the 0.1C capacity.

[0141] Five constant current charge-discharge cycles at 0.5C were performed, and the 0.5C capacity was recorded.

[0142] Five constant current charge-discharge cycles at 1.0C were performed, and the 1.0C capacity was recorded.

[0143] Five constant current charge-discharge cycles at 2.0C were performed, and the 2.0C capacity was recorded.

[0144] Restored to 0.1C constant current charge-discharge cycle for 5 times, and recorded the 0.1C capacity.

[0145] Experimental data:

[0146] Table 5. Discharge specific capacity test data (mAh / g) of all-solid-state batteries at different rates

[0147]

[0148] in conclusion:

[0149] The test data in Table 5 reveal the decisive influence of the construction method of the ion transport network inside the battery on high-power performance.

[0150] Example 1 still achieved a capacity of 112.3 mAh / g at a high rate of 2.0C, demonstrating high rate performance. Example 3 (70% LAGP) achieved an even higher capacity of 126.7 mAh / g at 2.0C. This confirms that a high proportion of NASICON-type inorganic particles established efficient lithium-ion fast transport channels within the electrode and electrolyte layer. As the current density increases, battery polarization is mainly limited by ion migration rate; the composite material with high ionic conductivity effectively reduces concentration polarization and ohmic polarization.

[0151] The data for Comparative Example 4 (PVDF binder) presents a stark contrast. While its capacity is acceptable at a low rate of 0.1C (151.2 mAh / g), it rapidly declines to 15.3 mAh / g at 2.0C. PVDF, acting as an insulator between electrons and ions, coats the surface of the positive electrode active material, blocking the lithium-ion insertion / extraction pathway; ions can only be transported through point contacts between particles. During high-current discharge, this discontinuous transport path causes a sharp increase in internal resistance, resulting in a sudden drop in voltage to the cutoff voltage, preventing the battery from releasing its effective capacity. This invention, however, uses a composite solid electrolyte to replace PVDF, achieving omnidirectional ion conduction on the surface of the positive electrode particles and eliminating the ion blocking effect inside the electrode.

[0152] Comparing Example 1 with Comparative Example 5 (stepwise curing, 2.0C capacity 74.2 mAh / g) shows that the physical contact interface is a significant rate-limiting step at high rates. Stepwise curing results in higher interfacial contact resistance, leading to a larger overpotential when a large current passes through. The in-situ polymerization process of Example 1 achieves atomic-scale interfacial fusion, reducing interfacial charge transfer impedance and thus maintaining a higher discharge plateau voltage and capacity at high rates.

Claims

1. An all-solid-state battery employing a composite solid electrolyte, characterized in that, It includes a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector, which are stacked in sequence. The positive electrode active material layer comprises a positive electrode active material, a conductive agent, and a composite solid electrolyte as a binder. The solid electrolyte layer is a layered structure composed of the composite solid electrolyte; The composite solid electrolyte is a solidified material with a three-dimensional cross-linked network structure formed by in-situ photopolymerization of composite solid electrolyte precursor slurry after solvent removal; The solvent-free solid component of the composite solid electrolyte precursor slurry consists of the following components: Nanoparticles, comprising 30wt%-70wt% of the total mass of the solid components; Polyethylene glycol dimethacrylate crosslinking agent, the content of which accounts for 5wt%-10wt% of the total mass of the solid components; And the remainder of polyethylene glycol methyl ether methacrylate monomer, lithium bis(trifluoromethanesulfonyl)imide and photoinitiator; The total mass of the solid components is calculated as 100 wt%.

2. The all-solid-state battery using a composite solid electrolyte according to claim 1, characterized in that, In the positive electrode active material layer, the solid mass ratio of the positive electrode active material, the conductive agent, and the composite solid electrolyte is 85-92:2-5:6-10; The conductive agent is acetylene black.

3. The all-solid-state battery using a composite solid electrolyte according to claim 1, characterized in that, The thickness of the solid electrolyte layer is 20μm-40μm.

4. The all-solid-state battery using a composite solid electrolyte according to claim 1, characterized in that, The positive electrode active material layer and the solid electrolyte layer form a chemical bond at the interface through the in-situ photopolymerization reaction, thereby connecting the composite solid electrolyte in the positive electrode active material layer and the solid electrolyte layer into an integrated structure; and the Nanoparticles are uniformly dispersed in the three-dimensional cross-linked network structure.

5. The all-solid-state battery using a composite solid electrolyte according to claim 1, characterized in that, The all-solid-state battery is prepared by the following steps: To prepare the composite solid electrolyte precursor slurry, the components of the NASICON type... The nanoparticles, the polyethylene glycol methyl ether methacrylate monomer, the lithium bis(trifluoromethanesulfonyl)imide, the polyethylene glycol dimethacrylate crosslinking agent, and the photoinitiator are dispersed in a solvent; The positive electrode active material, the conductive agent and the composite solid electrolyte precursor slurry are mixed to form a positive electrode slurry, which is then coated onto the positive electrode current collector and dried at 50℃-70℃ to remove the solvent, resulting in a dry positive electrode layer containing unpolymerized double bonds. The composite solid electrolyte precursor slurry is directly coated on the surface of the dried positive electrode layer and dried under vacuum conditions to remove the solvent, thereby obtaining the dried solid electrolyte layer. The negative electrode active material layer is laminated onto the surface of the solid electrolyte layer, and a pressure of 0.5MPa-2.0MPa is applied under vacuum to make the layers in dense contact. While maintaining pressure, the laminated battery is irradiated with ultraviolet light to trigger the in-situ photopolymerization reaction, causing cross-linking and curing to occur simultaneously inside the positive electrode active material layer and the solid electrolyte layer.

6. The all-solid-state battery using a composite solid electrolyte according to claim 5, characterized in that, The photoinitiator is 2-hydroxy-2-methylphenylacetone; The amount of photoinitiator added accounts for 0.5wt%-2.0wt% of the total organic monomer mass in the composite solid electrolyte precursor slurry.

7. The all-solid-state battery using a composite solid electrolyte according to claim 5, characterized in that, The drying temperature under the vacuum conditions is 50℃-60℃, the vacuum degree is less than -0.09MPa, and the drying time is 2-6 hours.

8. The all-solid-state battery using a composite solid electrolyte according to claim 5, characterized in that, The negative electrode active material layer is a lithium metal foil with a thickness of 30μm-50μm, and the lamination is carried out in an environment of room temperature to 40°C.

9. The all-solid-state battery using a composite solid electrolyte according to claim 5, characterized in that, The ultraviolet light irradiation uses a light source with a center wavelength of 365nm and a light intensity of [missing information]. The illumination time is 10-30 minutes.

10. The all-solid-state battery using a composite solid electrolyte according to claim 1, characterized in that, The solvent is acetonitrile.

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